There is a developing need to be able to determine the presence of potentially hazardous dust on isolated surfaces. As noted above, this dust may be radioactive, chemically active under certain ambient conditions or toxic. One use for such a device would be in conjunction with the next generation fusion reactor which could produce a large amount of dust and possible ensuing safety hazards. For example, if beryllium dust is not constrained within set limits, explosions could occur in the presence of steam under certain conditions. Thus, a device is needed to detect dust on remote surfaces for future fusion reactors; however, such devices do not exist for hostile environments. The subject apparatus is an electrostatic device which provides a correlation between recorded counts and particle concentration. This leads to the object of this apparatus which is to measure the particle inventory in a wide range of environments including those where radioactive particles are present.